The answer is A: It was the first selfless thing she did.
Explanation for each option:
A. It was the first selfless thing she did. - This option suggests that Abigail's decision to leave and warn John Marsh was motivated by a sense of altruism or concern for someone else's well-being, marking a significant moment of character development. This interpretation highlights the importance of her action as a turning point in her character arc, where she acts out of selflessness rather than self-interest.
B. She realized she needed to leave her family. - This option implies that Abigail's decision was primarily driven by a personal need to distance herself from her family. While this could be a factor in her decision, it does not emphasize the selfless nature of her action, which is the key point of significance in the context of the question.
C. She realized she hated him. - This option suggests that Abigail's motivation was based on negative feelings towards John Marsh. However, this does not align with the idea of her action being significant due to its selflessness. If her decision were based on hatred, it would not be considered a selfless act.
Therefore, the most significant aspect of Abigail's action is that it represents her first selfless deed, highlighting a moment of personal growth and change.